1. Field of the Invention
The present invention relates to a micro-discharge truing device for truing a very fine or thin electrically conductive grindstone and a fine machining method using the device.
2. Description of the Related Art
Recently, for development of a micro-machine and the like, there have been demands for a machining technique to machine constituting fine components with high precision. As a machining method suitable particularly for making holes or channels in such fine components, an electrolytic in-process dressing grinding method (hereinafter referred to as ELID grinding method) has been noted.
In the electrolytic in-process dressing grinding method (ELID grinding method), a very fine electrically conductive grindstone using fine diamond grains, or a very thin electrically conductive grindstone is used, and the grindstone is electrolytically dressed to machine an article to be machined (workpiece). The method is characterized in that machining precision is high, high-quality surface roughness is obtained, and hard three-dimensional shaped components are relatively easily machined.
Even a very fine/thin grindstone to be applied to fine machining surely has an offset or a deflection during processing. Therefore, such offset or deflection needs to be removed by truing prior to application to a precision machining like ELID grinding machining.
However, in a metal bond grindstone for use in the ELID grinding machining, a bond material is very hard. Therefore in a conventional truing method, a correction efficiency is low, a correction precision is limited, and the application is difficult. Specifically, since the grindstone to be applied to the fine machining is very fine or thin (e.g., a diameter of 1 mm or less, thickness of 1 mm or less), by contact with a tool for mechanical truing, the grindstone itself is deformed, which causes a problem that a high-precision truing cannot be realized.
On the other hand, as a machining method of machining a workpiece with no contact therewith, electric discharge machining is known. In the machining method, the workpiece and a machining electrode are opposed to each other with a gap therebetween in an insulating machining liquid, and a short-time pulse arc discharge is repeated, to perform removal machining.
In the machining method, however, there are problems that (1) a shape of the electrode needs to be conformed beforehand to a desired machining shape, (2) precise position control is necessary to keep a constant interval between the electrode and the workpiece, (3) a large current pulse needs to be supplied between the electrode and the workpiece, and a large complicated power equipment is necessary, and (4) since the electrode shape is changed by consumption of the electrode, the electrode needs to be frequently replaced.